1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 * posix-clock.h - support for dynamic clock devices
4 *
5 * Copyright (C) 2010 OMICRON electronics GmbH
6 */
7#ifndef _LINUX_POSIX_CLOCK_H_
8#define _LINUX_POSIX_CLOCK_H_
9
10#include <linux/cdev.h>
11#include <linux/fs.h>
12#include <linux/poll.h>
13#include <linux/posix-timers.h>
14#include <linux/rwsem.h>
15
16struct posix_clock;
17struct posix_clock_context;
18
19/**
20 * struct posix_clock_operations - functional interface to the clock
21 *
22 * Every posix clock is represented by a character device. Drivers may
23 * optionally offer extended capabilities by implementing the
24 * character device methods. The character device file operations are
25 * first handled by the clock device layer, then passed on to the
26 * driver by calling these functions.
27 *
28 * @owner: The clock driver should set to THIS_MODULE
29 * @clock_adjtime: Adjust the clock
30 * @clock_gettime: Read the current time
31 * @clock_getres: Get the clock resolution
32 * @clock_settime: Set the current time value
33 * @open: Optional character device open method
34 * @release: Optional character device release method
35 * @ioctl: Optional character device ioctl method
36 * @read: Optional character device read method
37 * @poll: Optional character device poll method
38 */
39struct posix_clock_operations {
40 struct module *owner;
41
42 int (*clock_adjtime)(struct posix_clock *pc, struct __kernel_timex *tx);
43
44 int (*clock_gettime)(struct posix_clock *pc, struct timespec64 *ts);
45
46 int (*clock_getres) (struct posix_clock *pc, struct timespec64 *ts);
47
48 int (*clock_settime)(struct posix_clock *pc,
49 const struct timespec64 *ts);
50
51 /*
52 * Optional character device methods:
53 */
54 long (*ioctl)(struct posix_clock_context *pccontext, unsigned int cmd,
55 unsigned long arg);
56
57 int (*open)(struct posix_clock_context *pccontext, fmode_t f_mode);
58
59 __poll_t (*poll)(struct posix_clock_context *pccontext, struct file *file,
60 poll_table *wait);
61
62 int (*release)(struct posix_clock_context *pccontext);
63
64 ssize_t (*read)(struct posix_clock_context *pccontext, uint flags,
65 char __user *buf, size_t cnt);
66};
67
68/**
69 * struct posix_clock - represents a dynamic posix clock
70 *
71 * @ops: Functional interface to the clock
72 * @cdev: Character device instance for this clock
73 * @dev: Pointer to the clock's device.
74 * @rwsem: Protects the 'zombie' field from concurrent access.
75 * @zombie: If 'zombie' is true, then the hardware has disappeared.
76 *
77 * Drivers should embed their struct posix_clock within a private
78 * structure, obtaining a reference to it during callbacks using
79 * container_of().
80 *
81 * Drivers should supply an initialized but not exposed struct device
82 * to posix_clock_register(). It is used to manage lifetime of the
83 * driver's private structure. It's 'release' field should be set to
84 * a release function for this private structure.
85 */
86struct posix_clock {
87 struct posix_clock_operations ops;
88 struct cdev cdev;
89 struct device *dev;
90 struct rw_semaphore rwsem;
91 bool zombie;
92};
93
94/**
95 * struct posix_clock_context - represents clock file operations context
96 *
97 * @clk: Pointer to the clock
98 * @fp: Pointer to the file used to open the clock
99 * @private_clkdata: Pointer to user data
100 *
101 * Drivers should use struct posix_clock_context during specific character
102 * device file operation methods to access the posix clock. In particular,
103 * the file pointer can be used to verify correct access mode for ioctl()
104 * calls.
105 *
106 * Drivers can store a private data structure during the open operation
107 * if they have specific information that is required in other file
108 * operations.
109 */
110struct posix_clock_context {
111 struct posix_clock *clk;
112 struct file *fp;
113 void *private_clkdata;
114};
115
116/**
117 * posix_clock_register() - register a new clock
118 * @clk: Pointer to the clock. Caller must provide 'ops' field
119 * @dev: Pointer to the initialized device. Caller must provide
120 * 'release' field
121 *
122 * A clock driver calls this function to register itself with the
123 * clock device subsystem. If 'clk' points to dynamically allocated
124 * memory, then the caller must provide a 'release' function to free
125 * that memory.
126 *
127 * Returns zero on success, non-zero otherwise.
128 */
129int posix_clock_register(struct posix_clock *clk, struct device *dev);
130
131/**
132 * posix_clock_unregister() - unregister a clock
133 * @clk: Clock instance previously registered via posix_clock_register()
134 *
135 * A clock driver calls this function to remove itself from the clock
136 * device subsystem. The posix_clock itself will remain (in an
137 * inactive state) until its reference count drops to zero, at which
138 * point it will be deallocated with its 'release' method.
139 */
140void posix_clock_unregister(struct posix_clock *clk);
141
142#endif
143